1. Technical Field
The present invention relates to an image processing apparatus, an image displaying apparatus, and an image processing method.
2. Related Art
A projector as an image displaying apparatus (image projecting apparatus) can be installed easily and can display a large-sized image at low cost, which could not be obtained by liquid crystal displays. The projector projects an image onto a screen. Accordingly, when the positional relation between the projector body and the screen is changed, a characteristic of the projector is that the shape of a display image is changed. For this reason, recent projectors correct the shape of a display image, which is changed depending on the positional relation between the projector body and the screen, by making a geometric correction such as a keystone correction as an imaging process.
The projector displays a large-sized image by making light from a light source (lamp) incident on a light modulating device, synthesizing or extending and projecting an image by the use of an optical system, and focusing the image on the screen. The color of a display pixel on the screen corresponding to one pixel is expressed by superposing display sub pixels corresponding to plural sub pixels of primary color components. Accordingly, a phenomenon (pixel shift) that the display positions of the display sub pixels of the color components are shifted from each other occurs due to an installation precision of the light modulating device, an influence of temperature on expansion and contraction, chromatic aberration of components of the optical system, or the like, thereby deteriorating the image quality.
Therefore, for example, JP-A-8-102901 discloses a technique of making the keystone correction and making a correction of the pixel shift. In JP-A-8-102901, the position of the image on a liquid crystal panel, as the light modulating device, is shifted in parallel in the unit of pixels by shifting the time points of horizontal and vertical synchronization signals. By sequentially making the keystone correction and adjusting the time points of the horizontal and vertical synchronization signals, the keystone correction and the correction of the pixel shift are made.
However, in the technique disclosed in JP-A-8-102901, the parallel shift of the image position on the liquid crystal panel is carried out only in the unit of pixels and thus the deterioration in image quality due to the pixel shift may not be satisfactorily suppressed. In the technique disclosed in JP-A-8-102901, a circuit for making the keystone correction and a circuit for adjusting the time points of the horizontal and vertical synchronization signals are required, thereby enhancing the circuit size and elongating the delay time of the imaging process.